Process of forming a bellmouth on a metal tube



Jan. 7, 1941. O B Z I 2,227,820

PROCESS OF FORMING A BELLMOUTH ON A METAL TUBE Filed June 5, 1937INVENTOR 'ATTORNEY Patented Jan. 7, 1941 UNITED STATES PATENT OFFICEPROCESS or FORMING A BELLMOUTH ON A METALTUBE Application June 5, 1937,Serial No. 146,584

Claims.

The present invention relates to a novel process of flaring an end of ametallic tube and increasing the strength of the flared portion bythickening the wall section of the same.

5 The invention is particularly useful in preparing tubing for standardunion couplings of the type having opposed conical gripping surfaces,and to this end the invention has for an object to provide a flared endhaving smooth conoidal inner and outer surfaces adapted to serve asseats for such gripping surfaces.

My process is particularly adapted for flaring of steel tubing such asis used for fuel lines of motor driven vehicles. However, the inventionis not limited to such tubing but may also be applied to tubing of othermetal and for other purposes.

Heretofore, it has been the practice to flare the ends of steel tubingwithout increasing the thickness of the metal of the flared portions.The metal is apt to'be reduced in thickness and be rendered brittle bythe ordinary flaring processes, so that cracks are apt to develop at theflared ends particularly if the tubing is subjected to constantvibration in service.

I am aware that steel tubes have been flared and the flared ends foldedinwardly to form a double layered bell at the end of the tubing, butsuch folding of the metal merely provides an enlarged body to be grippedby the union coupling without increasing the strength of the tubing atthe neck of the flare where the fracture is most apt to occur.

It is an object of my invention to provide a process of flaring andthickening the wall of the flared portion without folding the metal uponitself, and to produce an increase in the crosssection of the metal atthe flared end which extends from and includes the neck of the flare.

Other objects and advantages of my invention will appear in thefollowing description of my preferred process and preferred means forcarrying out the same and thereafter the novelty and scope of myinvention will be pointed out in the claims. I

In the accompanying drawing;

partly diagrammatic showing means for performing the flrststage of myprocess; 5 Fig. 2 is a view largely in longitudinal section of the endof a tube as it appears after having been subjected to said first stageof the process;

Fig. 3 is a view in longitudinal section of certain apparatus employedin performing the sec- 55 0nd and final stage of the process; and

Fig. 4 is a view in longitudinal section of a standard union fittingapplied to the finished tube.

In my flanging process I prefer to perform the first stage of theprocess with the metal heated and the second stage with the metal cold,although, as will be explained hereinafter, the entire process can beperformed in a single operation with the metal hot.

In Fig. 1, I show a piece of tubing III under- 10 going the first stageof the process. The tube is gripped by a pair of opposed electrodes IIand I2, each of which is provided with a semicircular socket I3 so thatwhen the two electrodes are in gripping position they will completelyen- 15 circle the tube. These electrodes are preferably made of copperor other material which is a good conductor of electricity and heat.

Immediately adjacent to the electrodes is a die of harder metal,preferably steel, which com- 20 prises a pair of jaws I4 and I5 eachformed with a diametric half of a bell shaped socket I6 so as tocompletely encircle the tube when the jaws are in closed position. Thejaws I4 and I5 may be directly connected to the electrodes 25 II and I2respectively, so that they will be closed simultaneously therewith. Whenthe die jaws are closed they grip the tube III at the inner end I1 ofthe socket. The latter is formed with an enlarged cylindrical portion I8at its 30 outer end and with an intermediate conoidal surface I9 whichis transversely curved at one end to merge into the gripping portion I1and at the other end to merge into the cylindrical surface I8. 35

Another electrode 20 is provided which has a conical end 2| adapted toenter the end of the tube I0, and, cut in the conical face of theelectrode, is an annular step forming a shoulder 22 adapted to engagethe inneredge of the end 40 of the tubing III, as shown in Fig. 1.Obviously, the conical portion of the electrode 20 need not necessarilybe carried to a point, but may be truncated if so desired.

Current is supplied to the electrodes from a 45 I g transformercomprising a primary coil 24 and a Figure 1 is a view in longitudinalsection and secondary coil 25. Oneend of thesecondary coil is connectedby a line 26 to the electrodes II and I2, while the other end of thecoil is' connected by a line 21 'to-the electrode 20. The transformer isenergized from a suitable source of alternating electric'current undercontrol of a switch indicated at 28. Y

In operation, the tubing I0 is gripped by the electrodes II and I2 andby the die jaws and the point of electrode 20 is inserted into the endof the tube so as to seat the inner end edge thereof against theshoulder 22. Current is now supplied to the electrodes and flows throughthe tubing in, heating that portion of the tubing which lies between thestep 22 and the electrodes 1 I and i2. The tubing is thus softened bythe heat developed therein. Pressure is then applied to cause relativeapproach of electrode 20 to electrodes l l and I2, with the result thatthe heated portion is bent substantially to the form shown in Fig. 2. Inother words, it bulges outwardly between shoulder 22 and the point whereit is gripped by the die jaws. The tube will be hotter intermediate itspoints of contact with the electrodes because of the high thermalconductivity of said electrodes which chill the metal at said points, sothat the tube will be bulged between said points and forced into contactwith the conoidal surface I! of the die. The outer extremity of thetubing is thereby turned inwardly by reason of its engagement with theshoulder 22 and the end face 29 of the tubing is given a conical form bythe conical face of the electrode 20.

In the first stage of the process it will be observed that the thicknessof the tube wall is increased toward the end due to the compressiveforces exerted. As shown in Fig. 2, the neck of the flared portion ofthe tubing is formed exteriorly in longitudinal section on the radius Awhile the inner surface of the tubing is curved on a radius B whichexceeds the radius A by an amount considerably greater than the normalthickness of the tube wall. It will be noted also that the thickening ofthe tube wall starts from the very neck of the flared portion.

It is desirable to further thicken the end of the tubing so as to extendthe surface 29 and this may be done by continuing the inward pressure ofthe electrode 20 until the tubing assumes the form shown in Fig. 3.However, I have found that better results have been obtained byperforming this stage of the process with other apparatus while thetubing is cold. By so doing, I am able to obtain smoother inner andouter surfaces to be gripped by the union couplings. The second stage ofthe operation is shown in Fig. 3. The bulged end of the tubing as formedby the first stage, is gripped in a steel die consisting of opposed jaws32 and 33 which completely encircle the tubing. This die is providedwith a socket very similar in form to the socket [6 shown in Fig. 1,having a conoidal surface 24 adapted to give the outer side of theflared end a smooth seating surface 35 for the union coupling. A punch36 formed with a frusto-conical end 31 is introduced into the end of thetubing. This tubing in its original bulged form is shown in dot and dashlines. As the punch 26 is forced inwardly with respect to the die 32 and33 a thrust is developed substantially normal to the face 29, and themetal is compressed until it forms a thickened head 32 with an extendedconical seat 2911 substantially parallel to the conical seat 25.

Fig. 4 illustrates the tubing with a standard union coupling connectedthereto. This coupling consists of a tubular member 40 of substantiallythe same bore as the main body of the tubing, such member being formedwith a threaded socket ll into which a nipple 42 is screwed. At theinner end of the socket there is a protruding annular lip 42 of conicalform adapted to seat against the face 29a of the head 38. The nipple'true seat with the conical tool 36.

42 is provided at its inner end with a conical seat 44 adapted to fitagainst the conical surface 35 of the flared end of the tubing. Thenipple 42 is screwed into the socket ll until the head 38 is firmlygripped therebetween. It will be observed that the gripping surfacesbear against a thickened portion of the tubing III which is not formedby folding the metal back upon itself but by plastically deforming themetal to increase its integral thickness. With the tubing thus formedthere is no tendency for cracks or fractures to develop because thetubing is actually stronger at its flared end than elsewhere and thisincrease of strength includes the neck of the flare as well.

It is of utmost importance that the conical seat 29a be true, since itis intended to fit the conical face of lip 43 accurately so as to form afluidtight joint therewith. It will be noted that unlike structures inthe prior art which form a conical seat on a side surface of the tube,my process forms a conical seat on an end surface of the tube. The endsurface is formed initially by severing the tube from a length of tubingand in the ordinary commercial practice this surface is true enough tostart with to insure the formation of a However, were the seat formed ona side surface of the tube initial irregularities in said surface mightnot be ironed out by the forming tools. For instance, in a tube having aseam forming either a ridge or a hollow on the inside or the outside orboth, such irregularity might leave a trace in the conical seat whichcould be eliminated only by a separate finishing process. With myprocess irregularities of the inner or outer surfaces of the tube do notin any way affect the final conical seat because this seat is formed onan end surface which is substantially true to start with. Thus, myprocess may be applied to seamed as well as seamless tubing withoutresorting to a separate finishing or truing operation.

Having thus described my invention what I claim as new and desire toprotect by Letters Patent is as follows:

l. The method of forming an outwardly flaring conoidal seat interiorlyon the end of a tube which consists in seizing the tube and restrainingradial expansion thereof at a point spaced from the end of the tube toprovide suflicient tube material for the formation of a bulge adjacentthe end of the tube, in heating and softening the tube adjacent its endleaving the end of the tube relatively cool and hard, and in applyingpressure normal to and only on the inner circumferential section of theend face of the tube to cause the wall of the tube adjacent the end ofthe tube to bulge outwardly and the end face to turn inwardly.

2. The'method of forming an outwardly flaring conoidal seat interiorlyon the end of a tube which consists in seizing the tube and restrainingradial expansion thereof at a point spaced from the end of the tube toprovide sufficient tube material for the formation of a bulge adjacentthe end of the tube, in heating and softening the tube adjacent its endleaving the end of the tube relatively cool and hard, and in applyingpressure normal to and only on the inner circumferential section of theend face of the tube to cause the wall of the tube adjacent the end ofthe tube to bulge outwardly andthe end face to turn inwardly against aconoidal die.

3. The method of forming an outwardly flaring conoidal seat interiorlyon the end of a tube which consists in seizing the tube and restrainingradial expansion thereof at a point spaced from the end of the tube toprovide suflicient tube material for the formation of a bulge adjacentthe end of the tube, in heating and softening the tube adjacent its endleaving the end of the tube relatively cool and hard, in applyingpressure normal to and only on the inner circumferential section of theend face of the tube to cause the wall of the tube adjacent the end ofthe tube to bulge outwardly and the end face to turn inwardly against aconoidal die, and in pressing a conoidal die against said inturned endface to thicken the wall of the bulged portion of said tube.

4. The method of forming an outwardly flaring conoidal seat interiorlyon the end of a tube which consists in seizing the tube and restrainingradial expansion thereof at a point spaced from the end of the tube toprovide suflicinet tube material for the formation of a bulge adjacentthe end of the tube, in heating and softening the tube adjacent its endleaving the end of the tube relatively cool and hard, in applyingpressure normal to and only on the inner circumferential section of theend face of the tube to cause the wall of I the tube adjacent the end ofthe tube to bulge outwardly and the end face to turn inwardly, and inlimiting the radial dimension of said bulged portion by expanding saidbulged portion against a cylindrical die surface.

5. The method of forming an outwardly flaring conoidal seat interiorlyon the end of a tube which consists in seizing the tube and restrainingradial expansion thereof at a point spaced from the end of the tube toprovide sufficient tube material for the formation of a bulge adjacentthe end of the tube, in heating and softening the tube adjacent its endleaving the end of the tube relatively cool and hard, in applyingpressure normal to and only on the inner circumferential section of theend face of the tube to cause the wall of the tube adjacent the end ofthe tube to bulge outwardly and the end face to turn inwardly, and inshaping the side of the bulged portion adjacent the point at which thetube is seized by expanding the same against a conoidal die OTTO J.BRATZ.

